If you need to use iframe to display youtube video on your website, tracking starts and pauses via analytics can be easily done.
The main trick is to add enablejsapi=1 into url.

E.g.
<iframe width=”560″ id=”somevideo” height=”315″ src=”https://www.youtube.com/embed/aCpGA7OrwyI?autoplay=1&enablejsapi=1″></iframe></pre>

becomes

<iframe width=”560″ id=”somevideo” height=”315″ src=”https://www.youtube.com/embed/aCpGA7OrwyI?autoplay=1&enablejsapi=1“></iframe></pre>

Now you can easily use the API. Feel free to use following example

<iframe width="560" id="somevideo" height="315" src="https://www.youtube.com/embed/aCpGA7OrwyI?autoplay=1&enablejsapi=1"></iframe></pre>

<script>
var player;
function onYouTubeIframeAPIReady() {
    player = new YT.Player( 'somevideo', {
        events: { 'onStateChange': function(state){
            if(state.data){
                if(state.data == YT.PlayerState.PAUSED){
                    // paused
                    ga('send', 'event', 'somevideo', 'paused', creativecoffeebreak.getCurrentTime());
                } else if(state.data == YT.PlayerState.PLAYING){
                    if(!playedAlready){
                        playedAlready = true;
                        ga('send', 'event', 'somevideo', 'start', creativecoffeebreak.getCurrentTime());
                    }
                } else if(state.data == YT.PlayerState.ENDED){
                    ga('send', 'event', 'somevideo', 'finished', creativecoffeebreak.getCurrentTime());
                }
            }
        } }
    });
}

</script>
<script src="https://www.youtube.com/iframe_api"></script>

Please note that the YT.PlayerState.ENDED doesn’t work in almost any browser.
Also, the “PAUSED” event is triggered when fast forwarding as well.

You need to load iframe_api javascript, otherwise the YT object won’t exist.